Double moving column grinder with simultaneous two wheel grinding

ABSTRACT

A grinding machine for grinding bulky workpieces of considerable length, such as frames, columns and tables of machine tools. Said grinding machine comprises at least one machining table on which a workpiece to be ground is placed, at least two columns linked to a single carriage, said carriage moving longitudinally over a base parallel to said machining table, and at least one wheelhead affixed to each of said columns, each one of said wheelheads comprising its own independently operated vertical and transverse drive means and at least one of said wheelheads being capable of angle movement. So, said wheelheads have a common longitudinal movement and independent vertical and transverse movements, so that said wheelheads can work simultaneously.

[0001] The present invention is a Continuation-In-Part (CIP) of theoriginally filed U.S. patent application Ser. No. 09/816,604.

TECHNICAL FIELD

[0002] The present invention relates to machines for grindingworkpieces, and more specifically to machines for grinding suchworkpieces as frames, columns and tables of machine tools.

PRIOR ART

[0003] The grinding of bulky workpieces of considerable length such asframes, columns and tables of machine tools requires the use of twodifferent types of wheelheads: tangential wheelheads and angle-movementwheelheads (so-called universal wheelheads).

[0004] The use of conventional flat grinders with a single column forgrinding workpieces of this type is well known. For this purpose,besides using the wheelhead mounted on the grinding machine column,another carriage with another wheelhead is fitted to the side of saidcolumn, said additional wheelhead generally having angle movement. Themachining table moves in relation to the column during the grindingprocess. This kind of grinding machines cannot work with both wheelssimultaneously.

[0005] The use of bridge grinders for grinding workpieces of this typeis also well known. Bridge grinders are grinding machines with twoopposing columns, one on either side of a machining table, and linkedtransversely by a cross rail. Two wheelheads are mounted on said crossrail, each of said wheelheads having its own vertical drive means andits own transverse drives means (up to a limited travel), and one ofsaid wheelheads generally being capable of angle movement. The crossrail may be fixed or vertically movable. During the grinding process,the machining table moves in respect of the columns and the cross rail.This kind of machines cannot work with both wheelheads simultaneously,as, although said wheelheads have their own drive means, the actualmachine frame with the cross rail prevents the wheelheads from workingat the same time because they would have to cross over as the transversemovement of both wheelheads is effected on a single support bracket.

DISCLOSURE OF THE INVENTION

[0006] The object of the invention is to provide a grinder for grindingbulky workpieces of considerable length, such as frames, columns andtables of machine tools.

[0007] The grinding machine of the invention comprises at least onemachining table on which a workpiece to be ground is placed, at leasttwo columns linked to a single carriage, said carriage movinglongitudinally over a base parallel to said machining table, and atleast one wheelhead affixed to each of said columns, each one of saidwheelheads comprising its own independently operated vertical andtransverse drive means and at least one of said wheelheads being capableof angle movement. So, said wheelheads have a common longitudinalmovement and independent vertical and transverse movements, so that saidwheelheads can work simultaneously.

[0008] As both wheelheads work simultaneously, output is practicallydoubled. In fact, the total grinding time is the grinding time of thewheelhead that has the longer process, as the grinding time of the otherwheelhead is included in the grinding time of the wheelhead that has thelonger process.

[0009] Since it is the columns that move and the wheelheads have alltheir movements in relation to said columns, the grinding machine cangrind workpieces placed on different aligned machining tablesconsecutively. Thus, the machine can be grinding the workpiece of onemachining table, while the operator handles the workpiece of anothertable. In this way, the workpiece change time is nil.

[0010] On the other hand, taking into account the automatic workpiecechange, the space occupied by the machine is smaller than that of abridge machine and even less than a conventional grinding machine, asthe latter requires palletizing systems. Moreover, there is aconsiderable saving in costs especially in relation to the use of abridge machine. These and other advantages will become apparent in thedetailed description of an embodiment of the invention.

DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an elevational view of an embodiment of the machine ofthe invention.

[0012]FIG. 2 is a profile view of the embodiment of FIG. 1 according tosection II-II.

[0013]FIG. 3 is a profile view of the embodiment of FIG. 1 according tosection III-III.

[0014]FIG. 4 is a profile detailed view of the carriage and the base ofthe embodiment of FIG. 1.

DETAILED DISCLOSURE OF THE INVENTION

[0015] In the embodiment of FIGS. 1 to 4, the grinding machine 1comprises a machining table 11 on which a workpiece 12 to be ground isplaced, two columns 2 and 3 linked to a single carriage 8, said carriage8 moving longitudinally over a base 9 parallel to said machining table11, and one wheelhead 4 provided with a grinding wheel 6 and affixed tocolumn 2 and one wheelhead 5 provided with a grinding wheel 7 andaffixed to column 3. The wheelhead 5 has vertical drive means 50 (shownin FIGS. 1 and 3) and horizontal drive means 51 (shown in FIG. 3). Thewheelhead 4 has vertical drive means 40 (shown in FIGS. 1 and 2) andhorizontal drive means (not shown for clarity). The vertical drive means50 and the horizontal drive means 51 of wheelhead 5 are operatedindependently of the vertical drive means 40 and the horizontal drivemeans of wheelhead 4, an vice versa.

[0016] So, the wheelheads 4 and 5 have a common longitudinal movementaccording to a direction A (shown in FIG. 1), and independent verticaland transverse movements, so that said wheelheads 4 and 5 can worksimultaneously: the wheelhead 4 has a movement according to a directionB and a movement according to a direction C (shown in FIG. 2), and thewheelhead 5 has a movement according to a direction D and a movementaccording to a direction E (shown in FIG. 3).

[0017] The wheelhead 5 only has tangential movement. The movements thatsaid wheelhead 5 has in relation to the column 3 are the usual onespossessed by the wheelheads on flat surface grinding machines. FIG. 3shows the wheelhead 5 in three different positions. The wheelhead 4 iscapable of being moved also in an angular direction, which permits thegrinding of workpieces of widely varying shapes. Said wheelhead 4 is aso-called universal wheelhead and has all the movements possessed bywheelheads of this type. Angular movement of said wheelhead 4 isprovided by a rotary plate 4 a. FIG. 2 shows the wheelhead 4 in threedifferent positions. The columns 4 and 5, and consequently thewheelheads 4 and 5, are facing each other.

[0018] The workpieces to be ground are bulky items of considerablelength, not usually more than one meter wide, such as frames, columnsand tables of machine tools. The grinding wheels 4 and 5 are largediameter wheels (up to 600 mm) and have high-power servomotors. Thegrinding with both wheels is carried out at the same time with a singlenumeric control that works in two channels with specific software.

[0019] The movement of the carriage 8 over the base 9 is effected bymeans of a hydrostatic slideway 90, so as to be able to reach typicalconventional grinding speeds (30 m/min). With reference to FIG. 4, saidhydrostatic slideway 90 includes longitudinal guides 91 on which thecarriage 8 slides, said guides 91 having chambers 17 with oil underpressure for lubrication. With said oil under pressure the necessaryrigidity of machine 1 is achieved.

[0020] The hydrostatic slideway 90 enables considerable accelerationsand decelerations to be achieved and, furthermore, it ensures that themovement of the columns is uniform, thus preventing the appearance of abuckling effect in said columns. In the embodiment of FIG. 1 columns 2and 3 are linked at the top by means of a cross member 10 to preventsaid buckling effect. With the use of the hydrostatic slideway 90, saidcross member 10 is not necessary.

[0021] The longitudinal movement of the carriage 8 is governed by meansof a rack and pinion system. With reference to FIG. 4 again, a pinion 13is mounted on the axis of a reducer 16 that is fixed to the carriage 8.Said reducer 16 is actuated by a servomotor not shown). Said pinion 13is geared to a rack 14 that is fixed to the base 9. The servomotor turnsthe reducer 16 and the rotary movement of said reducer 16 is convertedinto linear movement of the carriage 8 by means of the pinion 13 and therack 14. An encoder placed in the servomotor controls the location ofthe carriage 8.

[0022] As the assembly formed by carriage 8, columns 2 and 3 and theirrespective wheelheads 4 and 5 move en bloc on base 9, it is possible toinstall various aligned machining tables 11, each with its respectiveworkpiece 12, along the whole length of the base 9 and parallel to saidbase 9. This means that the machine 1 may be grinding workpiece 12 ofone machining table 11, while the operator is handling the workpiece 12of another machining table 11.

What is claimed is:
 1. A grinding machine for grinding bulky workpiecesof considerable length, such as frames, columns and tables of machinetools, comprising: at least one machining table on which a workpiece tobe ground is placed; at least two columns linked to a single carriage,said carriage moving longitudinally over a base parallel to saidmachining table; and at least one wheelhead affixed to each of saidcolumns, each one of said wheelheads comprising its own independentlyoperated vertical and transverse drive means and at least one of saidwheelheads being capable of angle movement; thereby said wheelheadshaving a common longitudinal movement and independent vertical andtransverse movements, so that said wheelheads can work simultaneously.2. The grinding machine of claim 1, wherein said columns are facing eachother.
 3. The grinding machine of claim 1, wherein the movement of saidcarriage over the base is effected by means of a hydrostatic slideway.4. The grinding machine of claim 1, wherein the longitudinal movement ofthe carriage is governed by means of a rack and pinion system.